Continuity mistake: When Walter is being rescued from the room he was trapped in, through the hole in the wall, we see the outside of the hole and Walter's body is outside except for his legs, and we see the hands trying to pull him back. In the next shot inside the room, Walter is again inside except for his head and arms. It repeats several times. (01:28:30)
Suggested correction: This is incorrect. Walter and Lisa are wearing similar clothes, making it look like he is in both rooms at once. Instead, as he is almost completely in the other room, Lisa is close behind him.
Continuity mistake: Susan and Lisa are standing perfectly still for a long time awaiting the transformation of the possessed girl, yet Lisa's hair goes from being behind her back to over her front then back again when the possessed girl "wakes" up.
Continuity mistake: The hand of the possessed girl calling her father (the Devil) through the large mirror varies between being a normal hand with minimal makeup to closeup shots with it heavily laden with makeup and thick fingers.